The present application is based on and claims priority from the following Japanese Patent Application 2001-43058, filed Feb. 20, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine of a generator or the like to be mounted in a passenger car, a truck or another vehicle.
2. Description of the Related Art
Recently, as the quality of vehicles improves, vehicle AC generators to be mounted on engines are demanded to decrease magnetic noise during the operation thereof. On the other hand, as the electric load for safety devices or the like has been increasing, demand for increasing the output power of the AC generator has been growing. Therefore, it is desired to provide a compact, quiet and powerful vehicle AC generator at a low price.
In order to satisfy the above-need, various arrangements for decreasing noises have been proposed. For example, U.S. Pat. No. 5,122,705 (or its corresponding publication JP-A-4-8140) discloses a pair of parallel three-phase windings, one is a xcex94-connection winding and the other is a star-connection winding, in which the phase of the voltage induced in a phase-winding is xcfx80/6 different from another. The voltage induced in one phase-winding of one of the pair of three-phase-windings has the same phase as voltage across two phase-windings of the other of the pair of three-phase windings, while the phase of current flowing in each phase-winding is xcfx80/6 different from another, so that high frequency components included in the currents, which cause magnetic noises, can be cancelled or decreased by one another.
In the arrangement stated above, in order to equalize the voltage across two phase-windings of the xcex94-connection winding and the voltage across two phase-windings of the star-connection winding with each other, it is necessary that the number of turns of the xcex94-connection winding is {square root over ( )}3 times as many as the number of turns of the star-connection winding. However it is impossible to provide such an irrational number of turns. Therefore, in the three-phase windings, which generate different voltage from each other, circulation current flows from one of the three-phase winding that generates higher voltage to the other, output current decreases and temperature of the generator rises, resulting in low efficiency of the generator.
In order to reduce the above problems, the number of turns of both the three-phase windings is increased to provide a ratio that is approximate to 1:{square root over ( )}3. However, it can not prevent the AC generator from increasing in size and temperature rise.
U.S. Pat. No. 5,998,903 (or its corresponding publication JP-A-11-155270) discloses an arrangement in which electric conductors are bent and connected together to form an armature winding. However it is necessary for one group of phase-windings of the armature winding having number of turns different from another group of windings to have a different bent shape. Therefore, if the armature winding includes windings of different turns, the structure becomes so complicated that production cost may increase very much.
The present invention has been made in view of the foregoing problems, and an object of the invention is to provide a compact, powerful, highly efficient rotary electric machine at a low cost even if windings generating different voltages are included therein.
In order to solve the above stated problems, in a rotary electric machine according to the invention includes an armature winding is comprised of three first phase-windings that form a xcex94-connection winding having output ends and three second phase-windings that are respectively connected in series to the output ends to form a star-connection three-phase winding having output ends connected to a rectifier unit.
Because each phase-winding of the star-connection three-phase winding is connected in series to the xcex94-connection three-phase winding, circular current can be prevented even if the voltages induced by the plurality of three-phase windings are different from each other. Therefore, output power loss due to the circulation current can be eliminated. Therefore, a compact, powerful and highly efficient rotary electric machine can be provided.
Preferably, the above three-phase windings are mounted in the stator core so that the phase of current flowing in the first phase-windings is xcfx80/6 in electric angle different from the phase of current flowing in the second phase-winding. Accordingly, high frequency components that may cause magnetic noise can be cancelled by combining the plurality of three-phase windings.
It is also preferable that each of the plurality of phase-windings has the same number of turns. It is possible to provide the phase-windings in the same winding process. As a result, manufacturing facilities can be simplified and work efficiency can be improved, so that the production cost can be reduced.
It is preferable that the above armature winding is comprised of a plurality of electric conductors welded together. With this structure, coil ends of the armature winding can be formed uniform or regular, so that the resistance of the armature winding can be drastically reduced. In addition, bending and welding works can be simplified, resulting in simplification of the manufacturing facilities and in drastically reduced production cost.
It is preferable that each of the electric conductors has a rectangular cross-section. With this feature, the space factor of the conductors to the slot of the stator core can be improved, thereby reducing the resistance of the armature winding. In addition, the rectangular cross section makes the electric conductors stiffer, so that vibration thereof can be effectively prevented.
It is preferable that the output ends of the xcex94-connection winding are distributed at an end surface of the stator core in an angular range that is more than 180 degree. With this feature, wiring work at the output ends can be made easier, so that the productivity can be improved.
It is preferable that lead wires that form output ends of the plurality of three-phase windings are extended in radial directions so that they do not overlap one another. With this feature, the lead wires can be made shorter, so that the resistance of the armature winding can be reduced, and so that the lead wires can be prevented from vibrating.